When subjected to elevated temperatures, bag collectors of amorphous silica fabric loses most of its strength during heating as well as after heating. This is due in part to devitrification, in part to solid and gaseous contaminants about the fabric as well as a loss of lubricant between adjacent fibers due to burnoff. This invention provides certain metal coatings on amorphous silica fabric for bag collectors to decrease the effects of contaminants, slow the devitrification process, and to provide a gold coating lubricant which will act at high temperature to avoid some of the frictional wear on the fibers. Amorphous silica fabric, when so coated, also may be used as heat barriers, as flame shields, or for filtering hot gases to remove particulate matter and other contaminants.
A fabric formed of amorphous silica fibers was selected as most suitable for use at high temperatures in bag collectors because amorphous silica fibers will maintain their shape and not soften or melt up to about 1450.degree. C. They exhibit good, if not almost perfect, elasticity up to a temperature several times that of glass or otherwise desirable materials. An object of this invention is to provide a method of making such amorphous silica fabric useful at high temperatures by first thoroughly cleaning the fabric and then coating substantially every thread and fiber of such fabric with a thin coating of metal, such as gold, or a metal or combination of metals selected to resist certain high temperature conditions.
Other metals may be also applied as an added protection or as a second coating, over the first, which will act as an additional lubricant at high temperatures. Such a material is indium which has a liquidity from 156.16.degree. C. to about 2000.degree. C. Other metals useful as a second coating are bismuth and tin.